Sorry, I was writing that from a cell phone. Let me elaborate.
It's an accepted trope of action storytelling that the "hero" is a constant while the stories are built around enemies and/or supporting characters. Development of the character is given in his or her backstory, which explains how they became who they are. Most of their flaws are dealt with in this origin story.
To use Greg's example of Optimus Prime, both the animated and G1 version had a similar origin. They both started out young and naive, but their interactions with Megatron and exposure to evil made them into a mature leader. Greg is technically wrong to call Optimus Prime undeveloped.
However, in G1, his development was limited to a single episode (the flashbacks in "War Dawn"). We know Orion Pax had a live-changing encounter with Megatron that resulted in his near death and caused him to become Optimus Prime. But by the end of this single story, he is already the godlike Prime we know from other episodes.
TF:Animated told a similar story, but did so over the course of the entire series. This is what I meant about "stretching out" the origin story. Gargoyles was similar to TF:A. Weisman didn't have them wake up and adjust to modern times immediately in the first episode (unlike the Autobots in G1).
Does that make sense? I'm tired tonight.
However, we are focusing way too much on the development of main characters and multi-episode arcs. "Character development" can occur in a single episode. Take any episode of Batman: The Animated Series, even episodes where the villain was never shown again. The villain was fleshed out and given logical motivations in the course of one episode, with Batman as a mere device to resolve the plot. "Criminal Minds" does this in live-action. There is real character development present, even without arcs.
In this sense, "GI Joe" had a lot of character development (especially in season 2). But the storylines almost never carried over from one episode to the next, and sometimes the characters who got the most exposition were hardly even shown again.
It's a shame GI Joe got cut short .... say what you will about "GI Joe: The Movie", but there was an obvious arc planned for Lt. Falcon (al la Rodimus Prime), and it would've been great to see how he adjusted to filling his brother's boots. Unfortunately, DIC ruined our chances of ever seeing that happen.